This invention relates to interconnection circuitry. In particular, this invention relates to interconnecting I/O card busses with host system busses using interconnection circuitry.
Conventional systems, such as computers, servers, or other systems require I/O cards (e.g., control circuitry) to operate. I/O cards can monitor and control parameters such as voltage, current, and temperature to keep the system up and running. I/O cards typically operate at a much lower frequency than the processing and memory circuits of the system. Therefore, I/O cards may require a separate, slower clocking and data transfer scheme to operate. Accordingly, various specification standards have been developed to define methods for performing data transfer with these cards. I2C and SMBus specification standards, for example, define a two-wire bus system having a single data line (SDA) and a single clock line (SCL) used for serial data transfer.
As systems (e.g., server systems) have increased in size, the number of input/output (I/O) peripheral cards used in a system have also grown in proportion. As a result, the equivalent capacitance on the data (SDA) and clock (SCL) lines of two-wire bus systems has also increased. This is because the SDA and SCL lines of each I/O card connect directly to those on the system's backplane, resulting in a single large bus. The increased capacitance may present problems, making it difficult for designers to meet the rise and fall time requirements defined, for example, by the I2C and SMBus specifications.
Another problem that may occur relates to connecting and removing I/O cards from the backplane without having to power down the backplane (a procedure known as “hot swapping”). Typically, power supply lines and ground lines may be successfully hot swapped, but when other lines such as data and clock lines undergo hot-swapping, it may result in some sort of equipment or software failure, possibly even causing damage to the equipment.
It is therefore an object of the present invention to provide interconnection circuitry that can hot-swap data and clock lines of two interconnected devices.
It is also an object of the present invention to provide capacitive isolation among devices coupled together on a bus using interconnection circuitry.